The present invention relates to a process and apparatus for sterilizing raw vegetable products and, more specifically, for sterilizing dry herbs as well as spices to render them suitable for human consumption.
In the past, sterilization of agricultural food products of the type that are packaged and placed on shelves without any significant cooking or preservatives added has depended on the use of chemicals to kill bacteria that have accumulated and grown on or near the surface of the vegetable matter. Other processes have resorted to the use of more conventional steam treatments. The difficulty with the former of these practices is that the chemicals used have often left a residue that is undesirable or may in fact be environmentally hazardous when disposed of. One such chemical that has been widely employed is ethylene oxide but which has been suspected of being harmful at some concentrations. On the other hand, the steam processes have often resulted in significant losses in terms of the flavor of the product being treated or unacceptable changes in the appearance such as the color of a food product or in the moisture content thereof. Certain food products such as leafy herbs and certain spices are particularly susceptible to damage when subjected to the steam sterilizing processes of the prior art such as that disclosed in U.S. Pat. No. 1,061,443, granted May 13, 1913. In other processes, such as that represented by U.S. Pat. No. 4,255,459 of Mar. 10, 1981, the food product is treated at such high temperatures over extended periods, that there is little possibility for avoiding substantial losses of the volatile oils that contribute significantly to the taste and therefore the saleability of the product.
In other arrangements, such as that disclosed in U.S. Pat. No. 4,210,678, substantial physical manipulation, such as grinding and crushing, is employed, which essentially change the nature of the product not to mention its appearance and taste so that the natural appearance and taste of the product is substantially if not entirely lost.
Apparatus for sterilization of material for human use or consumption are commercially available and can be modified to be usable in the process and system of the present invention. See, for example, U.S. Pat. 4,062,646.
Other processes have consumed considerable amount of time to complete the processing of a selected quantity of raw vegetable material, thus rendering the processes substantially uneconomical, while other processes have not resulted in sufficient reduction in bacteria counts to render the product suitable for safe human consumption. This is particularly important where the product must have a sufficiently long shelf life.
The present invention overcomes the foregoing difficulties by providing an environmentally safe yet highly economical and efficient process for handling raw vegetable material such as spices and leafy herbs without sacrificing the appearance, flavor level or control of moisture content of the herbs while providing significant enhanced microbe reduction so that the product will be suitable for packaging and storage in a retail outlet.
In a preferred embodiment, the present invention provides a sterilizing process where the raw and at least superficially cleaned vegetable product is disposed in a first preheated container. Culinary, that is substantially clean, steam without conventional additives is injected into the container while the contents are being mixed for a brief period of no more than five minutes for a selected quantity. The stirring or mixing of the contents of the container during the injection of the sterilizing steam assists in shortening this sterilization process thus avoiding undue exposure to the sterilizing steam and/or heat which can produce the harmful results in terms of reduction of the volatile oils, moisture content and adverse effects on the appearance of the product. This is particularly important in the case of leafy herbs which are to be subsequently packaged without any significant treatment for sale to the ultimate customer, either in bulk or in smaller retail sale containers. As is well known, leaf type herbs and spices, such as bay leaves, thyme, basil, marjoram, oregano, sage and parsley, are sensitive to temperature changes and moisture differences. The product may be held in the first container for a selected time before being transferred to a second container which is being maintained at a low pressure and the interior of which is cooled by a cooling jacket. When the product reaches the selected temperatures in the second container, the product is discharged therefrom under fluid pressure admitted to the second container.
The apparatus and method of the present invention will not only provide extremely close control of the operating parameters used in the sterilizing process but also will achieve high production output and high energy savings.
The foregoing and other advantages will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings, in which: